1. Field of the Invention
The present invention relates to a radiation image capturing system.
2. Description of the Related Art
For example, a radiation image capturing system that performs radiation photography aiming at medical diagnostics is conventionally known as a radiation image capturing system that captures a radiation image of a photography target. The radiation image capturing system includes a radiation detector, and captures a radiation image by detecting radiation radiated from a radiation irradiation device and transmitted through a subject using the radiation detector. The radiation detector performs capturing of the radiation image by collecting and reading charge generated by the radiated radiation.
A technology for performing photography using a plurality of radiation detectors, for example, to photograph a large photography target such as a long photography target is known. For example, a technology in which storage phosphor screens of CR (Computed Radiography) cassettes are used as radiation detectors, and end portions of a plurality of adjacent CR cassettes (storage phosphor screens) overlap, so as to capture a radiation image of an elongated object is described in JP2004-160208A.
In general, when the radiation image is captured, the radiation is transmitted through the photography target, and scattering rays are generated. Thus, the scattered rays are included in the radiation transmitted through the photography target. Therefore, a grid that eliminates the scattered rays is provided between the photography target and the radiation detector so as to eliminate the scattered rays included in the radiation reaching the radiation detector. By eliminating the scattered rays, effects such as suppression of degradation of a contrast of the radiation image are obtained, and image quality of the radiation image is improved.
In the technology described in JP2004-160208A, an anti-scatter grid is arranged between the CR cassettes and a patient that is the photography target to cover all of the plurality of overlapping CR cassettes.
In the case where the end portions of the radiation detectors overlap and photography is performed as described above, a shadow of the radiation detector on the upper side (a side close to a radiation irradiation device) may be shown as a step image in the radiation image captured by the radiation detector on the lower side (a side far from the radiation irradiation device).
Further, in the case where such photography is performed, a plurality of grids are jointed and used. In the case where the plurality of grids are jointed together and used, a joint of the grids is projected on the radiation detector. Accordingly, a joint image caused by the joint of the grid may be shown on the captured radiation image.
Therefore, both the step image and the joint image may be included in the radiation image. The step image is corrected through image processing, but in the case where both the step image and the joint image are included in one radiation image, correction of the step image and the joint image cannot be appropriately corrected, and image quality of the radiation image may be degraded.